Thirteen people, including children, were killed after a fire broke out on Tuesday in a Muslim school in Yangon due to a suspected electrical fault, police in Myanmar's main city said.

Thirteen people, including children, were killed after a fire broke out on Tuesday in a Muslim school in Yangon due to a suspected electrical fault, police in Myanmar's main city said.

The blaze comes against a backdrop of heightened Buddhist-Muslim tensions in Myanmar following recent sectarian clashes, but police said initial indications suggested that the blaze was accidental.

"Thirteen people, mostly children, were killed during a fire at a Muslim religious school in downtown Yangon," a police officer at the scene said. "We assume that it was due to an electrical short circuit."

Firefighters extinguished the blaze, which broke out in the early hours of Tuesday morning, he said.

Police called for calm and promised to establish a committee – including Muslim leaders – to look into the cause after an angry crowd gathered at the scene demanding answers, according to an AFP reporter.

The building housed a mosque and a religious school where children were staying while taking a summer class. Local residents said the victims were believed to be orphans.

A second police officer said the 13 dead were among more than 70 people sleeping at the school when the fire broke out.

"The rest of the children were rescued," he said.

The Myanmar Police Force reported on its official Facebook page that the victims died from burns or smoke inhalation.

"According to the investigation by township police officers, the fire was caused by excessively high (electric) voltage," it added.

Safety standards are generally poor in impoverished Myanmar, which is emerging from decades of military rule.

A wave of sectarian violence that began on March 20 has left 43 people dead and mosques and homes burned in several towns in central Myanmar, prompting the government to impose emergency rule and curfews in some areas.

Yangon has been tense but mostly peaceful following the clashes, which were apparently triggered by an argument in a gold shop that triggered a riot which later spread.

The conflict poses a major challenge for Thein Sein, who has won international praise for his reform efforts since taking office two years ago.

The situation has calmed in recent days after the former general on Thursday vowed a tough response over the violence, which he blamed on "political opportunists and religious extremists".

Sectarian strife involving Buddhists and Muslims in the western state of Rakhine last year left at least 180 people dead.